1. Field of the Invention
The present invention relates to a high-frequency heating apparatus such as a microwave oven, and more particularly, it relates to a high-frequency heating apparatus which allows continuous drive of a high frequency generator at the maximum high frequency output only under a predetermined time condition.
2. Description of the Background Art
In a conventional microwave oven, a magnetron serving as a high frequency generator is driven by high voltage power which is supplied through a high-voltage transformer and a high-voltage capacitor having prescribed rated values, or the like. The magnetron is cooled by a cooling device, which is formed by a fan or the like, while the same is driven by the high voltage power. Therefore, even if the magnetron is continuously driven for a long time for heating food etc. at the maximum high frequency output, the magnetron is effectively cooled by the cooling device and prevented from abnormal temperature rise. Such a conventional microwave oven is disclosed in Japanese Utility Model Publication No. 55-50504, for example.
In order to improve the performance of such a microwave oven for reducing its heating time, on the other hand, the maximum high frequency output itself may be increased. To this end, the rated value (capacitance value) of the high-voltage capacitor for supplying high tension power to the magnetron may be increased. When the high frequency output itself is thus increased, the cooling power of the cooling device must be improved since the heating value of the magnetron is also increased.
In order to improve the cooling power, however, it is indispensable to increase the size of the cooling device itself. Thus, the microwave oven is entirely increased in size and cost.